GDP seeds? I hope you get a good test.. I am currently backcrossing my Kens GDP clone to itself, I am at 87.5% (bx2), it is VERY dense herb and many outdoor guys say it`s great because it almost never molds. I will post more picts later.
It gets purple with nighttime temps in the 40s. I would not think it will purple much as an indoor plant. Hopefully your GDP will purple up nicely, I almost got those GDP seeds you are talking about to test them myself.
Anyway, I don't know who takes credit for GDP seed company but I know I dont like Ken Estes very much, I had a few conversations with the guy and if anyone says they have another form of Granddad's Purp from the 70s, he jumps on their asses with false accounts and spam.
I hope your GDP looks 10x better than mine, shove it down his throat. lol